A glioma is a collective term for tumors arising from neural stem cells, neural precursor cells, and neuroglial cells (glial cells). Gliomas account for approximately 25% of primary brain tumors in Japan, and are representative of malignant brain tumors. Moreover, gliomas are classified into astrocytic tumor, oligodendroglial tumor, oligoastrocytic tumor, ependymal tumor, and the like according to cells from which the gliomas are originated. Furthermore, gliomas are evaluated by grades from 1 to 4 according to the clinical malignancy established by WHO. Incidentally, grade 4 tumors are the most malignant and the prognosis is the worst, and particularly tumors of grades 3 and 4 are called malignant gliomas.
The treatment of the malignant gliomas is based on a surgery with adjuvant therapy of radiation therapy and chemotherapy, but has not changed much for several decades. Particularly, no effective treatment method for the most malignant glioblastoma multiforme (GBM) of malignant gliomas of central nervous system tissues has been found.
For this reason, searching is in progress for novel molecules, which could be targets of treatment and diagnosis for gliomas. So far, there has been reported, for example, that a DBCCR1L gene is specifically expressed in a glioma derived from oligodendrocytes (PTL 1).
Meanwhile, a single-pass transmembrane-type cell membrane protein Eva1 (epithelial V-like antigen, also called MPZL2) is a molecule involved in a cytoskeletal system, and is known to be expressed in a thymus and the like. Moreover, it has been reported that this protein is expressed in small-cell carcinoma (SCC), metastatic small-cell lung carcinoma (SCLC), pancreatic cancer, papillary throid cancer, and so on (NPLs 1 to 4).
However, no report has been made regarding a relation between Eva1 and gliomas at all.
Moreover, Ceacam1 (CARCINOEMBRYONIC ANTIGEN-RELATED CELL ADHESION MOLECULE 1) is a member of the carcinoembryonic antigen (CEA) family, and is known to regulate cell adhesion via homotypic binding and heterotypic binding to other CEA proteins. Further, Ceacam1 is believed to be involved in cell proliferation, inhibition of the cytotoxicity of immune cells, VEGF-induced angiogenesis, apoptosis, metastasis, as well as regulation of innate immune response and adaptive immune response (NPLs 5 and 6).
Furthermore, it has been shown that Ceacam1-L, one of splicing variants of Ceacam1, encodes an immunoreceptor tyrosine-based inhibitory motif at the cytoplasmic tails and demonstrates a tumor-suppressing activity based on this motif (NPLs 5 to 7). Meanwhile, there is also a report that the expression of Ceacam1-L is promoted in lung, colorectal, and thyroid cancers (NPLs 8 to 11).
As described above, it is not clearly understood what function Ceacam1 demonstrates in lung cancer and the like. Particularly, the association with gliomas has not been analyzed sufficiently until now.